Fatty Liver Disease (MASLD): Causes, Tests, and Treatment

An ultrasound for something else showed "fatty liver". Or your liver tests came back a bit high. You feel fine, so you may wonder if it matters. For many people it is mild. For some, it can lead to scarring. This guide explains the new name, the tests clinicians use, and what helps.

What MASLD is

MASLD stands for metabolic dysfunction-associated steatotic liver disease. Steatotic means fatty. In 2023, international liver societies chose this name to replace NAFLD (nonalcoholic fatty liver disease) [1].

You have MASLD when there is extra fat in the liver and at least one metabolic risk factor [1]:

• Extra weight or a large waist
• Prediabetes or type 2 diabetes
• High blood pressure
• High triglycerides
• Low HDL cholesterol

The stages

• MASLD: fat in the liver
• MASH (metabolic dysfunction-associated steatohepatitis): fat plus inflammation and liver cell injury. This used to be called NASH.
• Fibrosis: scarring caused by long-term inflammation
• Cirrhosis: severe scarring that can lead to liver failure or liver cancer

A related term, MetALD, describes people with MASLD who also drink a moderate amount of alcohol [1].

MASLD is very common, especially in people with type 2 diabetes or obesity [6]. Most people with MASLD do not develop cirrhosis. Heart disease is a more common cause of death than liver disease in people with MASLD [2].

What your doctor looks at

Scarring is the key question

The amount of scarring predicts long-term liver problems best [2]. Liver enzymes such as ALT can be normal even when scarring is present. So clinicians use other tests.

Step 1: the FIB-4 score

The 2023 American Association for the Study of Liver Diseases (AASLD) guidance suggests a FIB-4 score as the first step [2]. FIB-4 uses your age, two liver enzymes (AST and ALT), and your platelet count, all from routine blood tests.

• FIB-4 below 1.3: low risk of advanced scarring. Repeat in a few years if risk factors continue [2].
• FIB-4 of 1.3 or higher: a second test is suggested [2].
• FIB-4 above 2.67: higher risk, and referral to a liver specialist is often advised [2].

FIB-4 is less accurate under age 35 and can be higher in people over 65.

Step 2: liver stiffness tests

The most common second test is vibration-controlled transient elastography, often called FibroScan [2]. It uses a probe on the skin to measure how stiff the liver is. Stiffer livers have more scarring. It is quick and painless. A blood test called ELF is another option in some places [2].

Who should be checked

The AASLD suggests checking for advanced scarring in people with type 2 diabetes, people with two or more metabolic risk factors, people with fatty liver on imaging, and people with raised liver enzymes [2].

Liver biopsy

A biopsy is now used much less often. It may be needed if the diagnosis is unclear or other liver diseases need to be ruled out.

Treatment

Weight loss and lifestyle

Weight loss is the main treatment [2]:

• About 5% weight loss can reduce liver fat.
• About 7% to 10% can reduce inflammation.
• 10% or more may improve scarring.

Other steps [2]:

• Regular physical activity, which helps even without weight loss
• Limiting or avoiding alcohol
• Treating diabetes, high blood pressure, and cholesterol. Statins are safe for most people with MASLD and lower heart risk.
• Not smoking

Medicines

In March 2024, the US FDA approved resmetirom (Rezdiffra) for adults with MASH and moderate to advanced scarring, but not cirrhosis, along with diet and exercise [4]. In the MAESTRO-NASH trial, MASH resolved without worse scarring in about 26% to 30% of people on resmetirom compared with about 10% on placebo [3]. Scarring improved in about 24% to 26% compared with 14% [3].

Semaglutide, a GLP-1 medicine, was tested in people with MASH and moderate or advanced scarring [5]. After 72 weeks, MASH resolved without worse scarring in 62.9% on semaglutide compared with 34.3% on placebo. Scarring improved in 36.8% compared with 22.4% [5].

Approval status and coverage of these drugs differ between Health Canada and the FDA. Ask your clinician or pharmacist what is approved and covered where you live.

MASLD and the rest of your health

MASLD is closely tied to other metabolic conditions. The AASLD guidance advises that people with MASLD also be checked and treated for related problems [2]:

• Type 2 diabetes and prediabetes
• High blood pressure
• High cholesterol and triglycerides
• Sleep apnea
• Heart disease risk

Treating these helps both your liver and your heart.

Questions to ask your clinician

• Do I have MASLD, MetALD, or another liver condition?
• What is my FIB-4 score?
• Do I need a FibroScan or another stiffness test?
• How much weight loss would help my liver?
• How much alcohol, if any, is safe for me?
• Am I a candidate for a liver medicine?
• How often should my liver be rechecked?

When to get care quickly

Get urgent care for:

• Yellow skin or eyes
• Vomiting blood or black, tarry stools
• A swollen belly with fast weight gain
• Confusion or severe drowsiness
• Severe belly pain

Bottom line

MASLD is common and often mild, but some people develop liver scarring. A FIB-4 score from routine blood tests, followed by a stiffness test if needed, helps find who is at risk. Weight loss, activity, and less alcohol are the core of treatment, and new medicines now help some people with MASH.

Primary AI can show you the guideline and study sources behind this topic in plain language, so you can bring better questions to your appointment.